The invention relates to a dry-running vacuum pump with at least one vertically disposed shaft which is mounted in a top bearing plate by means of a lubricated rolling bearing situated in an open-topped pot-like component.
"Dry-running" vacuum pumps are pumps whose pump chambers contain no lubricant or sealants. Their advantage lies in the fact that they can produce vacuums completely free of hydrocarbons. However, it is impossible to dispense with the lubrication of the bearings of the shafts which bear the pistons rotating in the pump chambers. In dry-running pumps, therefore, it is necessary to assure an effective separation of the bearing chambers from the pump chambers.
A dry-running twin-shaft vacuum pump of the kind described above is disclosed in U.S. Pat. No. 290,662. To achieve separation of the upper bearing chambers from the adjacent pump chambers it is proposed to equip the upper ends of the shafts with an open-topped, pot-like component which traps bearing grease issuing from the bearings. The rolling bearings situated within the pot have a rotating outer ring which is held on the inner wall of the pot-like component. The stationary inner ring rests on a stump affixed to the housing and reaching into the pot-like component. In this system--in comparison with ordinary shaft bearings--there is a separate component between the shaft itself and the bearing ring rotating with the shaft, so that additional seams are present which can impair any correct shaft guidance.
The present invention is addressed to the problem of creating a vacuum pump of the kind described above, in which despite the presence of a pot-like component at the upper end of the shaft any interference with the shaft guidance described above will be avoided.